An AM radio or AM tuner particularly installed in a car to receive amplitude-modulated electromagnetic waves through its antenna suffers impulse noise from the ignition of your own car or cars of others, tram noise from tramcars or motor noise from electrically driven cars. In order to reduce such impulse noise components, a noise canceller is conventionally often used (see Japanese Unexamined Patent Publication No. 2000-10463). The noise canceller is provided with an automatic gain control (AGC) circuit which compensates fluctuations in electric fields of receiving signals to securely detect noise components on the basis of a reference voltage.
Since AM input signals in particular, however, vary their amplitudes, the input signals cannot be sufficiently separated from irregular impulse noise at the detection of noise components on the basis of a reference.
The present invention provides an AM radio or AM tuner with the reduction of impulse noise mixed in receiving signals.